This invention relates to pillared interlayered clay molecular sieve (PICMS) products and methods of their preparation. These products can be used as hydrocarbon conversion catalysts, absorbents and catalyst carriers. More particularly, the present invention relates to cross-linked regularly interstratified mineral clay (RIMC) products and methods of their preparation.
Until now, prior PICMS products were all cross-linked smectites type molecular sieve products prepared from smectites clays. PICMS products prepared from clays other than smectites have never been reported in the literature.
The smetites is a type of single layer mineral clay which is represented by the general formula: ##STR1##
The smectites clay group includes motmorillonite, bentonite, beidellite, hectorite, vermiculite and the like. Their characteristic designation is basal spacing (d.sub.001) of 9-15 .ANG. for air dried samples.
The cross-linked smectites type PICMS products are prepared by insertion of organic cross-linking agent or inorganic polymeric cationic hydroxy metal complexes into interlayers of smectites and to prop open the two adjacent 2:1 clay layers of the swelling smectites. Thereby a unique internal micropore structure, surface area and catalytic activity are created.
Although the cross-linked smectites type PICMS products have the advantage of great versatility in adjusting pore size, high catalytic activity for cracking large molecule reactants and are simple to prepare, their thermal and hydrothermal stabilities are poor. Under the conditions of the thermal or hydrothermal treatment, the props which serve to prop open the adjacent 2:1 clay layers of the smectites could be removed from the original prop points and cause 2:1 clay layers to collapse. It is apparent that the disintegration of pillars or 2:1 clay layers structure will make the micropore structure, surface areas and catalytic activities to deminish drastically. According to the literature the organic cross-linked smectites prepared by reacting smectites with organic amines could hardly withstand a thermal treatment at 250.degree.-550.degree. C. (Shabtai et al, Proc. 6th Inter. Congr. Catal., B5, 1-7, 1976; U.S. Pat. No. 4,367,163). Inorganic cross-linked smectites prepared by reacting smectites with polymeric cationic hydroxy metal complexes could only withstand treatment at 550.degree. C. (U.S. Pat. Nos. 4,216,188; 4,238,364).
In order to improve thermal and hydrothermal stabilities of cross-linked smectites type molecular sieve products, an improved method of preparing cross-linking agents were reported in the literature (U.S. Pat. Nos. 4,176,090; 4,248,739). Their thermal and hydrothermal stabilities were enhanced by said improved cross-linking agents, however the improvement is not good enough as the resulting product can only withstand treatment at 676.degree. C. with 5 psi steam for 8 hours.
So far, the thermal and hydrothermal stabilities of the PICMS product prepared by smectite clays is still an open question. Sample treated at 730.degree. C. with steam for 4 hours, 90 percent of its surface area and 80 percent of its pore volumes were lost. Its microactivities drop sharply from 80 percent to 30 percent (Occelli, M. L., I. and E.C. Prod. Res. and Dev., 22, 553, 1983).
All the data mentioned above have clearly indicated that the prior PICMS product is not as good as REY type zeolite catalysts with respect to high temperature stability in order to be used in catalytic cracking process. Hence no cracking catalysts from cross-linked smectites type PICMS products was ever used in commercial scale.
An object of the present invention is to develop another class of catalytic materials other than smectites and thereby to prepare a class of new PICMS with large pore size and excellent hydrothermal stability so as to improve the deficiency of prior PICMS of cross-linked smectites. Another object of the present invention is to provide the method of preparation and the application of said new PICMS.